In a radio communication system of Long Term Evolution (LTE) and LTE-Advanced (LTE-A), a technology has been known, which is called a centralized radio access network (C-RAN) and which is capable of accommodating a plurality of cells while suppressing a device cost so as to efficiently support an area such as a high-traffic hot spot.
The C-RAN is formed of one or a plurality of remote antenna units (RAU) which are remote installation type base stations (slave station), and a baseband unit (BBU) that is a base station (master station) that concentrically controls the RAU. The BBU has functions of Layer 1 to Layer 3 which are included in the base station. A digital baseband signal, which is generated in the BBU, is transmitted to the RAU, and is transmitted from a radio frequency (RF) function unit included in the RAU.
A network line that connects the BBU and the RAU is called a front haul (FH), and a common public radio interface (CPRI) is used as the FH in the LTE.